Carburetor



I May 13, 1941. H. A. CARLSON- CABBURETOR Filed Nov. 3, 1938- 2SheetsSheat 1 fnuenl' o r Harm/6 )q-aar/son MU-IZLQL flftorney y 13,1941- H. A. CARLSON 2,241,655

CARBURETOR 2 Sheets-Sheet 2 Filed Nov. 3, 1938 jrn/erlt'or Patented May13, 1941.

CARBURETOR Harold A. Carlson, University City,

to Carter Carburetor Corporation,

Mo., assignor St. Louis,

Mo., a corporation of Delaware Application November 3, 1938, Serial No.238,602

7 Claims. (Cl.261-41) This invention relates to carburetors for internalcombustion engines and consists, particularly, in novel means forpreventing gaseous bubbles formed in the main fuel passage or dischargenozzle from traveling upwardly through the nozzle and carryingunvaporized fuel into the mixture conduit.

Internal combustion engine carburetors are frequently exposed to suchhigh temperatures that the fuel in restricted spaces near the base oftheir fuel nozzles gasifies, forming bubbles which, when they havereached suflicient size, break loose from the surrounding metal and passupwardly through the fuel. Such bubbles formed during operation of thecarburetor and passing outwardly through the main nozzleresult in unevenoperation and excessive leanness, a condition known in the art assurging. After the engine has stopped. the heat thereof may risesufficientiy, due to stopping of the fan and water circulatiornto causesimilar gasiflcation and boiling or so-called percolation, in thecarburetor fuel passages and carrying of liquid fuel over the edge ofthe main nozzle. This action frequently continues until the bowl hasbeen run dry.

It has been suggested that percolation can be greatly restricted orstopped by the provision of a relatively large passage extendingvertically upwardly from the base of the main nozzle to the atmosphereand provided with a valve at its outlet end arranged to open when thecarburetor throttle valve is closed to release gases collected in thetop of the passage. The throttle controlled valve has been foundnecessary in order to prevent air from bleeding into the nozzle and tostabilize the fuel discharge from the nozzle. The valve has not provedwholly satisfactory, since it is difficult to prevent it from leakingand it increases the cost of the carburetor.

An object of the present invention is to provide an anti-percolatordevice which eliminates con- I trol valves, as described above.

Another object is to provide means for restricting or preventing surgingin carburetors.

' Another object is to provide an anti-percolator" device which isadapted also to function as an anti-surge" device.

These objects and other more detailed objects hereafter appearing areattained substantially by the structures illustrated in the accompanyingdrawings, in which 1 Figs. 1, 2, 3 and 4 are verticaltransverse'sectional views illustrating carburetors embodying differentforms of the invention.

Fig. 5 is a similar view showing a portion of a carburetor embodyingstill another modification.

The carburetor hown in each of the figures is is of the downdraft typeincluding an air inlet horn I, choke valve 2 therein, venturis 3, mixingchamber 4 and outlet portion 5 flanged as at 6 for attachment to anassociated internal combustion engine (not shown). A throttle valve 1 ismounted between the mixture chamber and outlet portion. Adjacent thecarburetor barrel is a bowl 9 within which fuel is maintained at asubstantially constant level by the usual needle valve mechanismcontrolled by float l0. Fuel is supplied from the bowl to the barrel ormixture conduit through a calibrated metering orifice member II, andpassage 12 opening into a normally submerged chamber 13 which forms thelower part of main nozzle l4 extending upwardly at an angle and openinginto the throat of the upper, smallest venturi 3. A relatively largepassage or well 15 extends more sharply upwardly from chamber I3 thanthe main nozzle, in the present case, vertically, above the normal fuellevel. Fuel for idling is supplied through passage l6 communicating atone end with passage i2 and at its lower end with port i1 adjacent andpartly posterior to the edge of the throttle valve, when closed. Theupper two venturis 3 are supported from the wall of the mixture conduitby rib structure I8.

In Fig. 1, a passage or duct 19 opens into main nozzle l4 slightly abovethe fuel level and extends upwardly and outwardly through rib l8 and thewall of the mixture conduit. A cross passage 20 connects passage IS withwell l5 and also with the mixture conduit. Calibrated restrictions 2|and 22 are provided in the cross passage. In other words, the outletportion of both the main nozzle and venting passages are co-extensivewhereby both passages communicate with the same suction zone in themixture conduit.

In operation, passage l9 and main nozzle ll will be exposed tosubstantially identical pressure conditions, but the height of crosspassage 20 above the fuel level and the relative sizes of the nozzle andrestrictions 2| and 22 in the cross passage are proportioned so thatnormally the pressure at the top and base of well IE will approach abalanced condition and little or no fuel will be drawn into the mixtureconduit through passage l9. Gaseous bubbles forming in chamber l3 at thebase of the main nozzle tend to take the easiest passage upwardlythrough well l5 instead of through the sloping, relatively small mainnozzle. Well I5 is large enough to and anti-surge passage is formed bymeans of a tube 25 Secured in plug. 26 at the top of well l5, extendsthrough the wall of the mixture conduit, and terminates at the outlettip of the main nozzle. No air bleed is provided in well l or tube 25,the height of cross passage 20 above the fuel level and restriction ofpassage tube 25 being relied upon to minimize the quantity of fuel drawninto the mixture conduit through the tube. I In Fig. 3, well l5communicates with the middle of second venturi 3 by means of a passage30 opening into the well above the normal fuel level therein. The outletend of passage 30 is in a relatively high suction zone, though at times,exposed to slightly higher pressure during operation of the carburetorthan the outlet tip of the main nozzle and, consequently, there may be atendency for air to bleed into the main nozzle through the passage andwell, particularly when the rate of flow is relatively low. Thisbleeding may be controlled or eliminated by calibrated restrictions, asat'Zl and 22 in Fig. l, and by proper positioning and shaping the outletend of the passage relative to the direction of. flow through themixture conduit and the inlet of the conduit. At high flows the suctionconditions at the outlet ends of nozzle [4 and passage 30 will approachbalance due to the blocking of the smallest venturi by'fuel emergingfrom the nozzle and consequent reduction of suction in this venturi.

In Fig. 4, well l5 communicates with the lowest or main venturi 3 bymeans of passage 32. This passage may also function, in some cases, asan air bleed which may be controlled by suitable calibratedrestrictions, (not shown) and by the inclination of the end of thepassage opening in the mixture conduit, as in the previous form. Asshown, this end is undercut or, in other words, faces in the directionof flow in the conduit which would tend to decrease the pressure in thepassage from that in the portion of the mixture conduit surrounding thisopening.

In Fig. 5, well [5 communicates with the mixture conduit by means of apassage 33 and tube 34 having an under-cut tip spaced slightly above theoutlet end of the main nozzle. Tube 34 functions to release gases inwell l5, as in the previous forms, and'also forms a shield for the mainnozzle which has a tendency to increase the suction applied thereto. Anadvantage of this'arrangement lies in a tendency to increase the fueldrawn from the main nozzle at periods of low suction when the throttlevalve is substantially 'opened.

In each form of the invention, any effect which the "anti-percolationpassage exerts upon the proportioning of the mixture may be controlledwithout loss of its primary function. Preferably, the pressureconditions in the well will be substantially balanced and it isparticularly important that fuel be prevented from draining from thewell or "dumped so that no air can bleed into the chamber l3therethrough. It is desirable that the vapor venting passage or ductextend to a higher level than the main nozzle, though not absolutelyessential since all fuel passing to the main nozzle is effectivelymetered through the metering jet in the fuel bowl. Various features ofthe carburetor shown are not essential and these may be modified in suchrespects as will occur to those skilled in the art withoutdeparting fromthe spirit of the invention. The exclusive use of all modifications ascome within the scope of the appended claims is contemplated.

I claim:

1. In a downdraft carburetor, induction conduit means, a constant levelfuel bowl, a chamber normally submerged in said bowl and communicatingtherewith through a metered orifice, a fuel nozzle extending from saidchamber to a portion of said conduit slightly above the normal level insaid bowl, a relatively large venting passage extending from saidchambermore directly upwardly than said nozzle and substantially higher thansaid nozzle, and a duct extending from the upper portion of said ventingpassage into said nozzle above the fuel level therein.

2. In a downdraft carburetoha mixture conduit including a venturi tube,a constant level chamber, a main fuel passage communicating with saidchamber through a metering orifice and extending upwardly into saidconduit, and a vapor venting passage having a part extending from thelower portion of said fuel passage posterior to said. metering orificesubstantially more directly upwardly than said fuel passage, both ofsaid passages leading into the throat of said venturi so as to besubjected to substantially identical suction conditions duringoperation, said vapor venting passage extending to a higher level thansaid fuel passage whereby the drawing of fuel through said ventingpassage is minimized.

3. In a downdraft carburetor, an induction conduit having a high suctionzone, an atmospheric constant level bowl, a main fuel passagecommunicating with said bowl through a metering orifice and extendingupwardly into said high suction zone, and a vapor venting duct for saidpassage, said duct including a relatively large portion extending fromsaid fuel passage posterior to said metering orifice more directlyupwardly than said passage, a vapor collecting portion above the fuellevel, and a pressure balancing portion leading into said conduit, saidduct extending to a higher level than said fuel passage and opening intosaid high suction zone.

4. A carburetor as specified in claim 3 further including an air bleedin said venting duct above the fuel, level and assisting'in reducing thesuction applied to the fuel therein.

5. A carburetor as specified in claim 3 in which the portion of saidventing duct below the fuel level is in the form of a vertical well ofsubstantially larger effective cross section than said fuel passage.

6. In a downdraft carburetor, means forming a mixture conduit having ahigh suction zone, a constant level fuel chamber, a main aspirating fuelpassage communicating with said chamber through a metering orificeleading upwardly at an angle into said conduit, and a vapor venting ductfor said passage, said duct including a relatively large portionextending from the lower part conduit, said main fuel passage and saidbalancing portion having outlet structure located substantially in saidhigh suction zone and disposed relative to the air flow in said conduitwhereby said duct is exposed to at least substantially as high suctionas said fuel passage during operation.

'7. In a downdraft carburetor, a mixture conduit having a high suctionzone, a constant level chamber, a main fuel passage extending upward- 1yat an angle from the lower part of said chamber into said conduit, therebeing a metering orifice in said passage, and a vapor venting ductcommunicating with thelower part of said passage posterior to saidorifice, said duct including a relatively large vapor releasing portionextending from said passage more sharply upwardly and to a substantiallyhigher"level than said passage and a balancing duct connecting said miX-

